1. Field of the Invention
The present invention relates to a printhead substrate, printhead, and printing apparatus.
2. Description of the Related Art
A printhead substrate can include a plurality of printing elements. The respective printing elements desirably have the same characteristics. For example, Japanese Patent Laid-Open No. 2007-022069 discloses a layout which equalizes voltages to be supplied to drive respective printing elements. Specifically, a transistor and resistor among circuits for generating such voltages are arranged at different positions. More specifically, the transistor is arranged in at least one of driving circuits (driver transistor, logic circuit, and booster circuit), and the resistor is interposed between the driving circuit and the side of a printhead substrate. According to Japanese Patent Laid-Open No. 2007-022069, this layout reduces the resistance component of a power supply wiring line, and equalizes voltages to be supplied to respective printing elements.
FIG. 14 shows the section of a printing element forming a heater HT. The heater HT can include an electric wiring layer 51, protective insulating film 52, and anti-cavitation film 53. An energy value necessary to drive the printing element can differ between printing elements owing to manufacturing variations such as differences in these film thicknesses between the printing elements. However, as a heat enable signal HE for driving the printing element, a common signal can be used for the entire chip or respective groups each including a plurality of printing elements. The load therefore differs between the printing elements.